Selective cation exchange in colloidal Janus-type Cu2-xS/CuInS2 heteronanorods for boosting photocatalytic hydrogen production

Ideal photocatalysis generally exhibits several key characteristics, including broad-spectrum light absorption, efficient electron-hole separation and transfer, excellent photocatalytic activity, and appropriate band alignment. To date, strategies for enhancing photocatalytic performance focus on surface modification, introduction of co-catalyst or doping, and heterostructure engineering. In this work, we aim to improve the photocatalytic activity of Cu2-xS by constructing heteronanostructure combined with ion doping. Through a two-step seeded-growth method, we successfully synthesized Janus-type Cu2-xS/CuInS2 heteronanorods with well-defined architectures for hydrogen production from solar water splitting. Three types of cations (Cd2+, Zn2+, Ga3+) were selected as dopants to further enhance the photocatalytic activity. Intriguingly, those foreign cations exhibit distinct doping behaviors in Janus-type heteronanorods, by either diffusing into Cu2-xS tips, CuInS2 tails, or across the whole nanorods. These selective doping behaviors originate from the miscibility of foreign cations with the parent nanocrystals and the lattice strain of possible products with respect to the template heteronanorods. The incorporation of foreign cations effectively alters the band alignment of the Cu2-xS/CuInS2 heteronanorods, thereby improving their photocatalytic hydrogen evolution performance. The Cd-Cu2-xS/CuInS2 heteronanorods exhibited excellent photocatalytic activity under visible light irradiation, with a hydrogen evolution rate of 1265.7 µmol·h-1·g-1, which is 83 times higher than that of the original Cu2-xS/CuInS2. This work provides new insights into the selective doping behavior in copper chalcogenide nanomaterials and opens up pathways for enhancing the hydrogen evolution activity of other related multicomponent photocatalysts.

Photoelectrochemical immunosensor for chloramphenicol detection based on cation exchange reaction-mediacted photocurrent enhancement of ZnIn2S4/TiO2/Ti3C2 MXene coupled with controlled-release strategy

A photocurrent enhancing photoelectrochemical (PEC) immunosensor was developed for chloramphenicol (CAP) detection based on cation exchange reaction. The efficient split-type PEC immunosensor combined with controlled-release strategy was established using the ZnIn2S4/TiO2/Ti3C2 MXene (ZIS/T/M) composite as the photoactive material and CuO as the signal response probe. In the presence of target CAP, CuO-labeled CAP antibody (CuO-mAb) was introduced onto the microplate via a competitive-type immunoassay. Under acidic conditions, a large amount of Cu2+ released from CuO-mAb, which triggered a cation exchange reaction with the Zn2+ in ZIS/T/M-modified photoelectrode to generate CuxS, resulting in enhancing the photocurrent. As a result, the quantitative detection of CAP was achieved by detecting the photocurrent change. Under optimized conditions, the linear range of the sensor was 1 pg/mL to 50 ng/mL, and the detection limit was 0.24 pg/mL. The excellent PEC behavior of ZIS/T/M composite could be attributed to the fact that heterojunction formation improved the migration and separation of the photocarrier. Additionally, by virtue of the photocurrent-enhancing strategy via cation exchange reaction and the controlled releasing signal amplification method of ion, the PEC immunosensor has high sensitivity and satisfactory accuracy, offering great potential applications in the determination of CAP.

Kinetically controlled morphology and composition of colloidal nanoparticles: cation exchange reactions from copper sulfide to transition metal (Mn, Zn, Fe, and Co) sulfides

The cation exchange reaction is a powerful method for generating nanomaterials with unique structures because of the easy control of the size, morphology, composition, and crystal structure of the nanoparticles. This study investigated the kinetically controlled morphology and composition of colloidal nanoparticles (NPs) through cation exchange reactions, specifically focusing on variations from copper sulfide to transition metal sulfides, including Co, Fe, Zn, and Mn sulfides. In the cation exchange reaction, Co exhibited the fastest exchange rate, followed by Fe, Mn, and Zn. The difference in kinetics rates affected the change in morphology; Co, with the fastest rate, was immediately and uniformly distributed in the NPs. For Fe, a sandwich structure was initially formed and this gradually transformed into a solid-solution phase. After exchanging Cu with Mn and Zn, a heterostructure was formed, which became increasingly clear as the reaction progressed. The transformation of the morphology and crystal structure were confirmed using XRD, TEM, and SEM analyses. The findings of this study suggest that the morphology and distinct structures of the exchanged particles can be controlled by manipulating the kinetics rates of cations through cation exchange reactions. This process offers a powerful tool for the tailored synthesis of colloidal nanoparticles and provides a design principle for enabling predictable outcomes through cation exchange reactions.

Colloidal Synthesis of γ-MnS Nanorods with Uniform Controlled Size and Pure ⟨002⟩ Growth Direction

One dimensional (1D) compound semiconductor nanostructures have unique anisotropic optical, electrical, and physical properties. Synthesis of large scale 1D nanostructures with pure crystallographic growth direction by a colloidal route and finding an easy method to prove it were significant for further exploring their unique anisotropic properties. Additionally, MnS is one of the most important optoelectronic and magnetic semiconductors. Herein, the large scale γ-MnS nanorods with completely pure ⟨002⟩ growth direction were first synthesized and convinced by solid evidence using the X-ray diffraction method. Compared with the standard diffraction pattern of γ-MnS powder, the ⟨002⟩ oriented long γ-MnS nanorods showed only the (100),(110), (200), and (210) peaks while other diffraction peaks disappeared. This study opened a door for the synthesis of the 1D colloidal nanostructures with pure crystallographic growth direction at large scale, benefiting the manufacture of a novel apparatus based on their anisotropic properties.

Amorphous CoSx decorated Cd0.5Zn0.5S with a bulk-twinned homojunction for efficient photocatalytic hydrogen evolution

Amorphous CoSx was combined with Twinned-Cd0.5Zn0.5S to construct homo-heterojunction for efficient photocatalytic H2 evolution. This work provides new ideas for constructing noble metal-free photocatalyst with homo-heterojunction.

Construction of Various One-Dimensional ZnS/MnS Heteronanostructures with Varied Diameters via the Multistep Solution-Solid-Solid Growth Method

A series of novel one-dimensional (1D) ZnS/MnS heteronanostructures were prepared by a multistep solution-solid-solid (SSS) growth method using [(C₄H₉)₂NCS₂]₂Zn and [(C₄H₉)₂NCS₂]₂Mn as the precursors and Ag₂S as the catalyst. The composition of the 1D heteronanostructures could be effectively modulated by varying the addition sequence of the precursors, such as the Ag₂S/MnS/ZnS and Ag₂S/ZnS/MnS heteronanostructures, which were obtained through the successive addition of [(C₄H₉)₂NCS₂]₂Zn and [(C₄H₉)₂NCS₂]₂Mn precursors but in different sequences. Using the same Ag₂S catalysts, the average diameter of the 1D ZnS/MnS heteronanostructures with multisegments of ZnS and MnS is located between that of ZnS nanorod in Ag₂S/ZnS and that of MnS nanorod in Ag₂S/MnS. This phenomenon could arise from the different cationic radii and lattice parameters of ZnS and MnS. The UV-vis absorbance of the 1D ZnS/MnS heteronanostructures could be attributed to the interband transitions of ZnS and MnS. These findings contribute to the rational synthesis of novel 1D semiconductor heteronanostructures with multicomponents and benefit the development of optoelectronic devices.